Probe systems of this kind are used, for example, for sensing the positions of workpieces that are clamped into material-working machines, such as milling machines. These probe systems often have a stationary part, which is secured to a fixed element of the material-working machines, and a part that is movable relatively thereto, which is often described as a measuring probe that is mounted on a movable element of material-processing machines, for instance on a milling spindle. In this context, the measuring probe includes a probe element that is deflectable out of a rest position and that generates a switch-on signal in response to a deflection out of its rest position. Rest position of the probe element is understood to be a position where the probe element does not have any contact with a workpiece. In response to contact of the probe element with the workpiece, the probe element is deflected out of its rest position.
In so-called wireless probe systems, such a switch-on signal is transmitted by the measuring probe as an electromagnetic signal, in particular as an infrared signal, to the stationary part. In this part, the output signals of the probe system are analyzed in order to determine the occurrence of switch-on signals (thus a deflection of the probe element).
Outside of the measuring operation times, the measuring probe is typically in a stand-by state. Shifting the measuring probe from its stand-by state to a measuring-operation state requires a power-up or activation process.
European Published Patent Application No. 1 130 557 describes a method for the wireless activation of a measuring probe. In this context, infrared light pulses are continuously transmitted at a predefined frequency from a stationary transmitting element of a probe system to a measuring probe. Because this method is not insusceptible to errors, the signal must be received for a certain time duration by the measuring probe in order to achieve an acceptable transmission reliability. However, if interference is also present within the frequency range in question during this time period, the measuring probe interprets the interference signal as an activation signal as well.
For this reason, it is an aspect of the present invention to provide a method for the wireless transmission of a control command from a transmitting element of a probe system to a measuring probe of a probe system that may be immune to interference and may be simple to implement.